Combustion-powered tools are known in the art, and exemplary tools produced by Illinois Tool Works of Glenview, Ill., also known as IMPULSE® brand tools for use in driving fasteners into workpieces, are described in commonly assigned patents to Nikolich U.S. Pat. Re. No. 32,452, and U.S. Pat. Nos. 4,522,162; 4,483,473; 4,483,474; 4,403,722; 5,197,646; 5,263,439; 5,897,043 and 6,145,724 all of which are incorporated by reference herein.
Such tools incorporate a tool housing enclosing a small internal combustion engine. The engine is powered by a canister of pressurized fuel gas, also called a fuel cell. A battery-powered electronic power distribution unit produces a spark for ignition, and a fan located in a combustion chamber provides for both an efficient combustion within the chamber, while facilitating processes ancillary to the combustion operation of the device. Such ancillary processes include: mixing the fuel and air within the chamber, turbulence to increase the combustion process, scavenging combustion by-products with fresh air, and cooling the engine. The engine includes a reciprocating piston with an elongated, rigid driver blade disposed within a single cylinder body.
A valve sleeve is axially reciprocable about the cylinder and, through a linkage, moves to close the combustion chamber when a work contact element at the end of the linkage is pressed against a workpiece. This pressing action also triggers a fuel-metering valve to introduce a specified volume of fuel into the closed combustion chamber. Thus, the valve sleeve opens the combustion chamber for venting gases, and closes the combustion chamber for sealing prior to ignition.
In such tools, once fuel is injected into the combustion chamber, the fuel and air are mixed using turbulence created by a rotating fan blade. If the fuel and air are not mixed properly prior to ignition, either a weak combustion cycle or no combustion will occur. Therefore, it is important that sufficient time is provided for mixing to assure repeatable nailer operation and desired performance. Mixing time is defined as the interval from which fuel is injected into the combustion chamber and the fuel and air is uniformly mixed.
The time duration for achieving complete mixture depends on many parameters, including fuel metering time, fuel spray pattern, fuel spray velocity, fan configuration and rotational velocity (RPM), and engine and fuel temperatures. Of these, the most significant are fan RPM, engine temperature and fuel temperature. The faster the fan RPM, the less time is required for mixing due to increased turbulence within the chamber. Considering higher tool and fuel operating temperatures, the gas molecules are more energetic, which in turn reduces available mixing time. In addition, higher fuel cell temperatures increase the pressure of the fuel, which gives the fuel spray/jet greater velocity as it is injected into the combustion chamber, which promotes mixing. The opposite trends of the previous conditions will cause increased required mixing times.
In view of the above conditions, there is a need for an improved combustion nailer configured for monitoring and controlling such parameters, and providing improved tool performance.